By} G. CARL HUBER 
this uterus. I am for the present unable to offer any plausible 
explanation or give reasons for such abnormal development of the 
segmentation cavity. The fate of such a structure may perhaps 
be conjectured from a study of the abnormal ovum shown in A 
of figure 6, interpreted as showing a similar abnormality, but ob- 
tained in early stages of degeneration. This ovum and that 
shown in B of the same figure was obtained from the uterus of 
rat No. 90, 6 days, 17 hours, after insemination. In the uterus 
of this rat there are found six ova, only one of which was de- 
veloped to a stage comparable to that shown in figure 24 (Part 
I) of about the same age. Three other vesicles present a slightly 
younger stage and may be compared with vesicles shown in 
D and E of figure 23, Part I. None of these four vesicles is 
favorably cut, but so far as may be determined, are of normal 
structure for the respective stages represented. A of figure 6 
is also cut slightly obliquely, not sufficiently so, however, to 
make difficult its interpretation. The figure drawn is that of 
the third of a series of seven sections having 10 » thickness, and 
depicts what is regarded as representing an ovum with abnormal 
segmentation cavity formation. In this ovum, the segmentation 
cavity is slightly more eccentric than is that shown in figure 5, 
and contains a granular detritus which in the preparations is 
distinetly stained with Congo red. The roof of this vesicle is 
composed almost throughout of more than one layer of cells. 
There is no differentiation of ectoplacental cone and ectodermal 
node, nor of yolk entoderm. Two cells regarded as phagocytic 
leucocytes, staining much more deeply in Congo red than do the 
cells of the ovum, have, in the section figured, penetrated the 
ege-mass, indicating early degenerative changes. 
The vesicle shown in B of figure 6, obtained from the same rat, 
is favorably cut, and is readily epllowed through the series. The 
structural appearance presented by this vesicle is not explained by 
supposing it due to very oblique plane of section of a normal 
vesicle, a plane of section which might include the roof of the 
vesicle while avoiding its floor. The vesicle is abnormal in that 
it presents a want of development of the thickened germ disc, 
and a hyperdevelopment of the yolk entoderm. In none of the 
